Morphological and Molecular Differentiation of Clinostomum complanatum and Clinostomum marginatum (Digenea: Clinostomidae) Metacercariae and Adults

Abstract

The separation of Clinostomum complanatum Rudolphi, 1814 and Clinostomum marginatum Rudolphi, 1819 has long been unclear. Recent data confirm the validity of the junior species, C. marginatum , by ∼ 1% differences in its 18S rDNA sequences. We collected adults and metacercariae of C. complanatum and C. marginatum and found reliable morphological differences in the genital complex at both developmental stages. In addition, we identified basic morphometrics (distance between suckers, body width) in metacercariae that may be useful for discriminating the species. The morphological differences were supported by the comparison of sequences of internal transcribed spacers of ribosomal DNA and of the mitochondrial gene cytochrome c oxidase I (COI) from 39 specimens. In 36 specimens, the average divergence between the species was 7.3% in ITS and 19.4% in COI sequences. Two specimens from North America and 1 from Europe had sequences that did not allow them to be clearly allied with either species.

Clinostomum album n. sp. and Clinostomum marginatum (Rudolphi, 1819), parasites of the great egret Ardea alba L. from Mississippi, USA

“…As with other groups of digeneans, discriminatory morphological characters that differentiate closely related species are lacking. This has led to an underestimation of true species richness, which was revealed primarily through molecular DNA sequencing (Caffara et al, 2011;Locke et al, 2015;Rosser et al, 2016a). Supplemental molecular data coupled with detailed morphological descriptions have facilitated the identification of new species and offer more sound support of amended descriptions of established species.…”

“…internal transcribed spacer regions) and mitochondrial (e.g. cytochrome c oxidase subunit 1) genes (Caffara et al, 2011;Gustinelli et al, 2010;Sereno-Uribe et al, 2013;Locke et al, 2015).…”

“…In Mexico, C. complanatum has been found in great egrets (Violante-González et al, 2012); however recently Sereno-Uribe et al (2013) suggested that previous records of C. complanatum in Mexico are likely C. marginatum or the more recently recognized Clinostomum tataxumui Sereno-Uribe, PinachoPinacho, García-Varela & Pérez-Ponce de León, 2013 from great egret, great blue heron, and barethroated tiger heron Tigrisoma mexicanum Swainson. Furthermore, Caffara et al (2011) combined morphological and molecular data to differentiate adult and metacercaria stages of C. complanatum and C. marginatum and concluded that C. complanatum is the ''European'' species and is not present in the Americas.…”

A review on the molecular characterization of digenean parasites using molecular markers with special reference to ITS region

“…To update the information, the present review is being presented here. As observed, ITS-1 and ITS-2 of rDNA provided trustworthy markers for molecular systematics along with mitochondrial DNA (Huang et al, 2004;Razo-Mendivil et al, 2004;Miura et al, 2005;Maurelli et al, 2007;Al-Kandari et al, 2011;Caffara et al, 2011;Huang et al, 2012;Bott et al, 2013;Presswell et al, 2014). Only 47 studies mentioned the intra-specifi c (0.05 -10.9 %) or inter-specifi c variations (0.01 -16 %) and inter-generic variations of 2.67 -21.0 %.…”

“…The molecular data corroborated the similarity between adult and metacercaria of C. cutaneum from bird and fi sh, respectively along with sequences of other Clinostomum sp. Caffara et al (2011) morphologically and genetically identifi ed Clinostomum complanatum and C. marginatum using the 18S, ITS and mitochondrial COI sequences. The average variability was 7.3 % in ITS and 19.4 % in COI sequences of both species and these molecular results affi rmed the morphological fi ndings.…”